My test was on browser only. Check your PHP.ini settings in CLI and in webserver for any differences.
The CLI output for php check.php is:
"{\"trans_type\":\"10\",\"ref\":\"NoGuia0001\",\"customer_id\":\"78\",\"branch_id\":\"78\",\"location\":\"DEF\",\"deliver_to\":\"ABC, S.A. DE C.V.\",\"delivery_date\":\"2019\\\/11\\\/09\",\"delivery_address\":\"Karachi\",\"order_date\":\"09\\\/11\\\/2019\",\"phone\":\"\",\"cust_ref\":\"\",\"comments\":\"\",\"ship_via\":\"1\",\"payment\":\"1\",\"sales_type\":\"1\",\"items\":[{\"stock_id\":\"2801\",\"description\":\"iPhone\",\"qty\":\"1\",\"price\":\"100\",\"discount\":\"0\"},{\"stock_id\":\"2802\",\"description\":\"Samsung\",\"qty\":\"1\",\"price\":\"100\",\"discount\":\"0\"}]}"